1. Field of the Invention
The present invention relates to a quadrature signal generator, and more particularly, to a quadrature signal generator which is capable of phase-tuning with respect to all of four generated quadrature signals.
2. Description of the Related Art
A quadrature signal generator generates four quadrature signals using two differential signals generated by a local oscillator. The quadrature signal generator is called “poly phase filter” (PPF).
The quadrature signal generator is provided with phase tuners. The phase tuner generates a quadrature signal by changing a phase of an incoming differential signal. The quadrature signal generator includes four phase tuners. Since the respective phase turners generate quadrature signals of different phases, the quadrature signal generator outputs four quadrature signals.
The phase tuner typically includes two input terminals to receive a homogenous differential or a heterogeneous differential signal, respectively.
However, if the homogeneous differential signals are input to each input terminal, it is impossible to tune phases of the quadrature signals. Also, if the heterogeneous differential signals are input to all of the two input terminals of the phase tuner, the amplitude of the quadrature signal is deviated from a reference value due to a signal unbalance occurring during the phase tuning process.